A cross sectional study was carried out at Kality wastewater stabilization ponds, in Addis Ababa from 4 may to 24 August 2009. The objective of the study was to evaluate the performance of the stabilization ponds and to assess the physico-chemical characteristics of the sludge. The plant comprised of facultative and maturation ponds in two series. Accordingly, Samples were taken from the influent, two facultative ponds effluent, last two polishing ponds effluent and the final effluent while sludge samples were taken from four piles of drying beds. Laboratory analysis was carried out following standard methods for the analysis of temperature, pH, conductivity, DO, BOD5, COD, TDS, TSS, S2-, SO4 2-, TN, NH4 +-N, NO3 --N, orthophosphate, TP, Total Coliforms, Fecal Coliforms, Cr, Pb, and Cd and for the sludge pH, moisture content, volatile matter, fixed carbon, ash, nitrogen (NO3 --N), total phosphorous (TP), potassium (TK), Pb, Cd, Cr. Results of this study showed that the average concentrations of BOD5, COD, TSS and TDS in the influent and final effluent were 290.1, 585.8, 212, 328.3; and 47.5, 131.4, 71.0, 294.7 mg/L respectively, with the removal efficiency of 83.6%, 77.6%, 66.5% and 10.3% respectively. The concentrations of NH4 +- N, NO3 - N, TN, Ortho-P and TP were 30.7, 1.13, 89.8, 11.7 and 14.6 mg/L respectively in the effluent and for the effluent their respective concentrations were found to be 16.2, 0.30, 37.3, 8.4 and 10.2 mg/l. The removal efficiency of the pond system for these parameters were 47.3% for NH4 +- N , 73.5% for NO3 - N, 58.5% for TN, 28.0% for Ortho-P and 30.1% for TP. The concentrations of NH4 +- N, NO3 - N, and TN were below the provisional discharge standards. But the concentration of total phosphorous was found to be slightly higher than the provisional discharge standards, which indicates the possibility of eutrophication in the receiving water body (little Akaki river). The reduction percentage of S2- was 96.3% and 66.2% for SO4 2-. On the other hand, the reduction percentages of Total Coliform (TC) and Faecal Coliform were 99.40 and 99.76 respectively, although the concentration in the final effluent was very high; 3.4×108 MPN / 100 ml and 2.7×107 MPN / 100 ml respectively. Regarding the physico-chemical properties of the sludge, its average pH was 6.58± 0.11 and the percentage of total phosphorous, total potassium and NO3 --N were 3.66 ± 0.38 %, 0.70 ± 0.08% and 0.04± 0.01% respectively, while the concentration of heavy metals (Cd, Cr, and Pb) was less than 20 mg/L in all samples. Based on the results of the study, the waste stabilization ponds system was found to be efficient in removing most of the pollutants of concern. But it is recommended to use further treatment options to remove TC, FC, total suspended solids and total phosphorous prior to discharge or reclaim the wastewater.